Real-world analog signals such as temperature, pressure, sound, or images are routinely converted to a digital representation that can be easily processed in modern digital systems. In many systems, this digital information is converted back to an analog form to perform some real-world function. The circuits that perform this step are digital-to-analog converters (DACs), and their outputs are used to drive a variety of devices. Loudspeakers, video displays, motors, mechanical servos, sensor actuation, instrumentation, radio frequency (RF) transmitters, and temperature controls are just a few diverse examples. DACs are often incorporated into systems in which real-world signals are digitized by analog-to-digital converters (ADCs), processed, and then converted back to analog form by DACs.
A DAC produces a quantized or discrete step analog output in response to a binary digital input code and the analog output is commonly a voltage or a current. To generate the output, a reference quantity, or level, (usually the aforementioned voltage or current) is commonly divided into binary and/or linear fractions. Segmented converters convert different parts, or segments, of the input in stages e.g. with most significant bits (MSBs) converted by a first stage or sub-block and least significant bits (LSBs) converted by a second stage or sub-block. Converters may also have modes utilising decision tree logic to decode the input and the converter may not be fully segmented, e.g., per U.S. Pat. No. 9,444,487.
Then the digital input drives switches that combine an appropriate number of these fractions to produce the output. The number and size of the fractions reflect the number of possible digital input codes, which is a function of converter resolution or the number of bits (n) in the input code.